Dehydration of tar, etc.



May 15,- 1934.

S. P. MILLER DEHYDRATION OF TAR, ETC

Filed March 14, 1927 4 Sheets-Sheet 1 NVENTOR WWW ATTORNEYS y 1934. s. PMILLER 1,958,583

DEHYDRATION OF TAR, ETC

Filed Marh 14, 1927 4 Sheets-Sheet 2 ATTORNEYS y 1934- s. P. MILLER,958,583

DEHYDRATION OF TAR, ETC

Filed March 14, 1927 4 Sheets-Sheet 5 Fig INVENTOR ATTORNEYS May 15,1934. s. P. MILLER DEHYDRATION OF TAR,

ETC

Filed March 14, 1927 4 Sheets-Sheet 4 INVENTOR MM hm BY fiw%m #WATTORNEYS Patented May 15, 1934 DEHYDRATION OF TAR, ETC.

Stuart Parmelee Miller, Tenafly N. 5., assignor to The Barrett Company,New York, N. Y., a corporation of New Jersey Application March 14, 1927,Serial No. 175,073

4 Claims.

This invention relates to improvements in the dehydration anddistillation of tar, and includes a new method of dehydration anddistillation as well as an improved apparatus therefor.

In the distillation of coal in coke ovens, etc.,

the coal distillation gases carrying the tar are commonly sprayed withammonia liquor or a mixture of ammonia liquor and tar to cool the gasesand separate the tar therefrom. The separated ,tar isadmixed withammonia liquor, and, even after standing to permit as much as possibleof the ammonia liquor to separate therefrom, may contain a considerableamount of water intimately mixed therewith. Long settling will in somecases reduce the water content to approximately two percent. Often,however, the water is emulsified and even long settling with moderateheating does not cause separation. In such a case the tar may contain ashigh as fifteen to twenty percent water.

When tar containing water is shipped from the coke oven or other coaldistillation plant to the tar distillation plant, the water content ofthe tar adds materially to the cost of transportation.

When such water-containing tar is subjected to dehydration, in ordinarystills, trouble from foaming is frequently met with even though the tarbe slowly and gradually heated in the still. It is best to subject thewater-containing tar to dehydration before distilling it, and specialdehydrators have been proposed for this purpose.

The present invention provides an improved method and apparatus fordehydrating tar, or for dehydrating and distillirn tar, whereby thedehydraton, or the dehydration and distiliation, are effected by meansof hot gases'produced by the same type of coal distillation operationsby which the tar is itself produced. The present invention makesunnecessary the consumption of fuel for heating and dehydrating, ordehydrating and distilling, the tar, and makes use of the heat alreadycontained in the high temperature coal distillation gases from the cokeoven, etc., by drawing off these gases while still at a high temperatureand employing them for heating and dehydrating, or dehydrating anddistilling, the tar.

The tar to be dehydrated, or dehydrated and distilled, accord'ng to thepresent invention, may be coal tar produced at coke oven plants, or gashouse tar produced at gas retort plants (vertical, horizontal orinclined), water gas tar, etc. Such tars frequently contain aconsiderable percentage of water intimately admixed or combinedtherewith, particularly where water or ammonia liquor is employed forseparating and condensing the tar constituents from the coildistillation or other gases.

The gases which are employed, according to the present invention, forthe dehydration, or w dehydration and distillation, of the tar, are hotgases produced by the coal carbonization or coal distillation operation.These gases may be hot coke oven gases, or hot gas retort gases, or hotwater gas, etc. .In the case of coke oven gases, for

example, the gases escape from the coke oven at a high temperature, forexample, around 600 to 700 C. or even higher in some cases. Hightemperature gases are also formed and are withdrawn from gas retorts,water gas retorts, producers, etc.

The gas employed for the dehydration, or dehydration and distillation,may be withdrawn at practically its maximum temperature, as it comesfrom the coke oven or retort, or the gas may be employed at a somewhatlower temperature, after it has passed through part of the byproductrecovery system, such as the collector main of the coke oven. The gasmay be cooled considerably below the original temperature, but 89 itshould be employed at a sumciently high temperature to exert the desireddehydrating and distilling action upon the tar to be dehydrated anddistilled.

By employing the gas while it is still at a high temperature, the heatwhich it contains is utilized for the dehydrating and distillation ofthe tar, while by bringing the hot gas into intimate contact with thetar, the vapors driven 01f from the tar by the dehydration anddistillation are admixed with the gases and may be subsequentlyseparated and recovered therefrom.

In carrying out the dehydration, or dehydration and distillation,according to the present invention, the distilling and dehydrating gasesare brought into heat interchanging relation with the tar to bedehydrated and distilled, and are advantageously brought into direct andintimate contact with the tar. This intimate contact of the tar andgases can be effected in various ways, and the dehydrating anddistilling operation can be carried out either as a batch operation oras a continuous operation. The tar to be dehydrated can, for example, beatomized or sprayed into a current of the hot gas, thereby bringing thetar particles into intimate contact with the hot gas and heating the tarparticles to a sufficient tem-- perature to dehydrate, or dehydrate andpartially distill, the tar. Instead of spraying or atomizing the tarinto a current of the hot gas, a current of the gas may be forcedthrough a body of the tar to be dehydrated, thereby heating andagitating the body of tar and effecting dehydration and partialdistillation of lighter oil constituents therefrom, which constituentsare carried by the escaping gases. 7 The dehydration and distillationcan also be effected in a counter-current manner, for example, bycausing the tar to be dehydrated to flow downwardly through a bafiietower or other apparatus in which an upward flow of the hot gases iseifected, so that the downwardly flowing tar is progressively heated anddehydrated and distilled, or the hot gases may be passed over thesurface of a body of tar, for instance, in a closed tank. In this caseit will be desirable, though not essential, to agitate the body of tarto keep fresh surfaces exposed to the gases.

The employment of hot coal distillation gases for the dehydration anddistillation of the tar presents the advantage among others, that thegases themselves are subjected to a scrubbing and purifying treatment bybringing them into contact with the tar to be dehydrated and distilled;while the lighter constituents driven off from the tar during thedehydration and distillation are ad- .rnixed with the remaininguncondensed constituents of the gases, and can be recovered therefrom bythe same subsequent condensing or recovery treatment. 7

Depending upon the extent to which the distillation of the tar iscarried, substantially only the light oils may be removed with the waterand free ammonia from the tar, or, by heating to a higher temperature,heavier oils can be driven off.

If, for example, the tar is heated, during the dehydration anddistillation, only to about 130 C.

only the lighter oils will be driven off therefrom during thedehydration and distillation; while if the tar is heated to a highertemperaturejheavier oil constituents will also be driven oil and will becarried away by the hot distillation gases and can be subsequentlycondensed and recovered therefrom.

By continuing the distillation, after the dehydration has beencompleted, progressively increasedamounts of oils can be removed untilonly a heavy tar, or in some cases a'pitch, remains.

The distillation can be accomplished in numerous ways. For example, alarge volume of relativelylow temperature gases may be used, or a smallvolume of relatively high temperature gases may be used. The tar may bepreheated if desired before introduction into the gas. In any event thetemperature of the gases leaving the dehydrator must always be heldabove the dew point for water since otherwise dehydration will not becomplete.

For certain purposes dehydrated tar containing 0.5% to 1% water isentirely satisfactory. The production of such tar may be accomplished atrelatively low gas temperatures, for example, approximately 125" C. orlower. If a tar containing no more than tracesoi water be desired, itwill be found expedient to work with gases at higher temperatures, forexample, approximately 160 to 170 C. Distillation as well as dehydrationwill be carried out at such temperature and the dehydrated tar will be aheavier tar, that is, it will contain less light oil, will be moreviscous and will have a higher specific gravity. If a more fluid tar bedesired, some of the oil distilled out may after recovery from the gas,be freed from water and be returned to the tar.

The gases escaping from the dehydrating and distilling operation willcarry in vapor form the water removed from the tar during thedehydration as well as the ammonia and the oils driven off from the tarduring the distillation. These gases will also contain such of the vaporconstituents carried thereby as have not been removed by contact withthe tar being dehydrated and distilled. In the case of hot coke ovengases, for example, these gases may be employed for the dehydration anddistillation of coal tar produced by the coke ovens and the hot gasesafter being employed for the dehydration and distillation will stillcontain uncondensed constituents as well as added vapor constituentsdriven oiT from the tar during the dehydration and distillation.

The gases containing such vapor constituents are treated for thecondensation and recovery of such constituents therefrom, as well as forthe recovery of ammonia carried thereby. Such gases can be treated in aseparate recovery system so that the oils condensed therefrom will bethe oil constituents remaining in the gases and those added to the gasesduring the distillation. In such case, the apparatus will have aseparate condensing and recovery system.

Instead of providing a separate condensing and recovery system, thegases from the dehydration and distillation can be returned to the maincondensing system and the vapor constituents and ammonia recoveredtherefrom along with the vapor constituents and ammonia carried by thecoal distillation gases with whichsuch gases are admixed.

The invention is of particular advantage for the dehydration, ordehydration and distillation, of coal tar at coke oven plants byutilizing the hot coke oven gases for the dehydration and distillation.The process is also advantageous for the dehydration of gas house tar,Water gas tar, etc. The dehydration, or dehydration and distillation,can be carried out in existing equipment or in special equipment. In acoke oven plant where several batteries of coke ovens are operated, allof the gas from one battery may be employed for dehydrating, ordehydrating and distilling, tar from the other batteries; or a part ofthe gases from one battery may be so employed. Such dehydration, ordehydration and distillation, can be carried out, for example, in thecollector main of such a battery in which case the dehydrating, ordehydrating and distilling, capacity of the gases in the collector mainwill be sufiicient to dehydrate, or dehydrate and distill, all of thetar from several other batteries. When an entire collector main, or partof a collector main, is so employed for dehydrating, or dehydrating anddistilling, tar, the'temperature of the main can be regulated andcontrolled and various expedients employed for bringing the tar intointimate contact with the hot gases to effect the desired dehydration,or dehydration and distillation.

The present invention enables dehydrated'tar to be produced, or tarwhich has been both dehydrated and distilled to a greater or less extentto remove oil constituents therefrom. Where the tar is desired in adehydrated condition, still containing the greater part of its oilconstituents, the dehydration can be carried only to the point necessaryto remove all or practically all of the water contained therein,together with such light oils as are removed at the same temperature.Where, however, a heavier tar is desired, the distillation can becarried further, until more of the light oils are removed, to give a tarsuitable, for

example, for use as a road tar for surfacing roads, etc. By continuingthe distillation, a heavier tar, or even a pitch, can be produced. Wherethe tar is to be separately distilled, in a separate still ordistillation system, the dehydrating process of the present inventioncan advantageously be carried out as a preliminary operation to give adehydrated tar. If the further distillation is car ried out at the sameplant at which the tar is produced and dehydrated, the hot dehydratedtar can be conveyed directly to the distillation system and subjected todistillation therein. The preliminary dehydration of the tar reducesmaterially the hazard of the distilling operation, for example, byreducing foam troubles.

Where the dehydration and distillation are carried out as abatchoperation, for example, by

forcing the hot gases through a body of the tar to be dehydrated, thetar will be progressively heated by the hot gases and the water andlighter oils will be progressively removed therefrom, until thedehydration and distillation have been carried to the desired point,after which the operation can be discontinued, the dehydrated anddistilled tar withdrawn, and the still recharged with tar to bedehydrated. In the case of continuous dehydration and distillation, theoperation can be regulated, by regulating the time of contact of the tarand gases, or the intimacy of contact, or the temperature of the gases,or the amount of the gases so that the desired degree of dehydration anddistillation can be effected.

The invention will be further described in connection with theaccompanying drawings, illustrating several forms of apparatus embodyingthe invention and adapted for the practice of the process of theinvention, but it is intended and will be understood that the inventionis illustrated thereby but is not limited thereto.

In the accompanying drawings, Fig. 1 shows, in a somewhat conventionaland diagrammatic manner, an elevation of part of a coke oven batterywith part of its by-product recovery system and with apparatus for thedehydration and c, distillation of tar by means of the hot coke ovenwhich may be substituted for the dehydrator in Figs. 1 and 2; and

Fig. 7 shows another form of dehydrator.

In the drawings, part of a coke oven battery is shown conventionally at1, having the usual uptake pipes 2 for the escape of the coke-oven gasesand the usual collector main 3 connected with the uptake pipes. Theusual center box for the collector main is shown at 4. The coke-ovengases escape from the collector main and center box through the vaporpipe 6 controlled by a valve 3 and the cross-over main 5 to the coolingand condensing system indicated conventionally as two condensers 7 and8. From these condensers the gases pass through the pipe 9 and the usualtar trap to the exhauster l0 and thence through the gas outlet pipe tothe tar extractor, ammonia saturators and benzol scrubbers, etc. (notshown).

In the collector main, the gases are somewhat cooled, for example, byammonia liquor sprays,

or tar and ammonia liquor sprays (not shown) and the condensed tar andammonia liquor collects in the center box 4 while the gases with someentrained tar and uncondensed vapors pass over through the cross-overmain 5 to the condensers I and 8.

An outlet pipe 11 is provided leading from the center box 4 for the tarand ammonia liquor which are conveyed therethrough to the decanter 12where some separation of the tar and ammonia liquor takes place. Thetar, after such settling and separation, will still contain appreciableamounts of water intimately combined or admixed therewith. This tar canbe conveyed either continuously or intermittently through a pipe 6controlled by a valve 13' to the dehydrating still l3 where itissubjected to dehydration. Valves 11 and 12 control the fiow of tar toand from the decanter 12. A gas pipe 14, which may be provided withinsulation (not shown) leads, preferably, from one end of the collectormain 3 to the dehydrator 13 and terminates, for example, in a cross pipe15 therein having perforations along its bottom side as best illustratedin Fig. 3. A valve 4 is provided in the pipe 14. The gas escapes fromthe dehydrator through the pipe 16 having valve 20 therein. The gaseswith admixed vapors may pass through the pipe 16 and the valve 20 to theseparate condensers 22 and 23 where condensation of vapors takes placeand then through a gas outlet pipe 19, having a valve 17 therein, and apipe 24 to the main gas outlet pipe 25. An exhauster 21 is providedbetween the pipes 19 and 24 to draw the gases through the dehydrator 13and the condensers 22 and 23, or the exhauster may be placed in pipe 14.A bypass 18 having a valve 18' therein permits the gas to pass aroundthe condensers when the valves 20, 1'7, 22, 17 and 18 are properlyadjusted. The gases from the dehydrator may be carried also to thecross-over main 5 through a pipe 21' controlled by a valve 22 foradmixture with the coke oven gases so that condensable constituentscontained in the gases from the dehydrator will be recovered in the mainrecovery system.

The dehydrated, or dehydrated and distilled, tar passes from thedehydrator 13 through the pipe 26 and may be delivered by a pump 27either through the pipe 28 to the tank 30 or through the pipe 31 to thetank 33, valves 29 and 32 being provided to control the flow throughthese pipes.

Tar collected in the condensers '7 and 8 can be withdrawn through pipes34 and 35 and delivered through a pipe 36 controlled by a valve 37 to adecanter 33. The tar is separated therein from the ammonia liquor andcan be delivered through a pipe 39 controlled by a valve 40 to thedehydrator 13.

In the apparatus illustrated, the by-product recovery system of the cokeoven battery can, for the mostpart, be operated in the ordinary way, buta part of the hot coke oven gases are drawn off and employed for thedehydration or distillation of the tar, and these gases and containedvapors are then subjected to separate condensation or are returned foradmixture with the main coke oven gases for condensation therewith.

In the collector main, the coke oven gases may be cooled by the ammonialiquor, or tar and ammonia liquor, spray, and the current of tar andammonia liquor flowing therethrough. Where this tar and ammonia liquorspray system cools the gases to a temperature below that at whicheffective dehydration of tar can be effected therewith, the ammonialiquor spray may be omitted or at least substantially reduced at the endof the main from which the hot gases are withdrawn, so that the gaseswill pass through the uptake pipes and into the end of the main and thenthrough the pipe 14 at a temperature not greatly below that at whichthey escape from the coke oven. In this way the gases can be employed ata high temperature where they have a high distilling capacity so thateffective dehydration, or dehydration and distillation, can be efiectedtherewith; By regulating the amount of ammonia liquor, or tar andammonia liquor, spray in the end of the collector main from which thegases are taken, the temperature of the gases can be regulated, but ingeneral it will be advantageous to draw off the hotcoke oven gases whilethey are still at a high temperature so as to ob tain effective heatingand dehydration and distillation of the tar therewith. These coke-ovengases will contain all on the greater part of the tar constituentsnormally contained therein. During the intimate contact of the hotcoke-oven gases with the tar to be dehydrated, the gases will bescrubbed and purified to a greater or ess extent from heavy tarconstituents, leaving in the gas proportionately more of the lighter tarconstituents, while the dehydration and distillation of the tar willdrive off from the tar the lighter .oils which will be carried alongwith the gases By subjecting the escaping from the dehydrator. gases toseparate cooling and condensation, a relatively clean oil can bedirectly obtained from the dehydration and distillation; while byrelturning the gases and admixed vapors to the main condensing system,the condensable constituents can be recovered without the need ofseparate condensing equipment and the resulting products will berelatively cleaner than those i normally obtained.

The dehydrator 13 as previously described may be replaced by a tower asillustrated in Fig. 6 of the drawings, wherein the tar is permitted toflow downwardly over a plurality of baffles so as to expose the maximumsurface of the tar to the hot gases ascending through the tower. In thisway advantage can be taken of the heating eiiect of the gases todehydrate the tarwithout retarding the gases or causing any appreciableback pressure or disturbing the balance of gaseous pressures in thesystem. Referring to Fig. 6, ll indicates a tower which may be of anysuitable form and construction and is preferably provided with aninsulating jacket (not shown) to i conserve the heat of the gasespassing therethrough. The tar accumulated in the decanter 12 isdelivered through an inlet pipe 42 to the top of the tower and flowsdownwardly over a plurality of bailles 43 arranged therein to facilitatethe exposure of the maximum. surface of the tar to the ascending gases.These gases may be withdrawn from the collector main 3 and deliveredthrough the pipe 14 as shown in Fig. 1 to the inlet 44 at the base ofthe tower 1. The

gases circulate upwardly around the baffles 43,

giving up their heat to the descending stream of tar, and escape throughan outlet 45 which may be connected to the pipe 16 as shown in Fig. 1.The dehydrated tar which accumulates in the bottom of the tower 41 iswithdrawn through a;

sufficient temperature may be obtained.

to the hot gases, it interposes no substantial resistance to the flow ofthe gases. It is, nevertheless, heated by the gases which, being at atemperature above the dew'point oi the gas for water, cause thevaporization of moisture in the tar and also, depending upon thetemperature and other conditions of operation, may remove some of themore volatile constituents of the tar. .jIhe latter can be condensed ashereinbefore described in connection with the condensation of vaporsfrom other gases flowing from the ovens, or a separate condenser systemcan be utilized to recover any valuable products in the gases whichleave the dehydrator.

In the modified form of dehydrator shown in Fig. '7, the operation issimilar to that in the dehydrator shown in Fig. 6, except that insteadof coming into intimate contact with the hot gases by passing overbaffle plates, the tar to be dehydrated is sprayed into the hot gaseswhich are introduced through the inlet 50. On ascending through thetower, the hot gases volatilize the low boiling constituents of theliquid which is introduced through the spray nozzles 51 so that the taris dehydrated, and depending upon the heat and quantity of the gases,etc., lowboiling constituents of the tar may be volatilized.

The treated tar collects in the reservoir 52 in the bottom of the towerand may be drawn off continuously or at intervals through the outletpipe 53, or, tar collecting in the reservoir 52 may be withdrawn :by thepump 54 and carried up through the pipe 55 and again subjected totreatment by the hot gases by being sprayed again through thenozzles'fil. Instead of recirculating the tar, the nozzles may besupplied by fresh tar introduced through the pipe 53 or tar may beintroduced to the nozzles through both pipes 53 and 55 at one time, orby using separate feed 7 pipes certainnozzles may be supplied withtreated tar while other nozzles are supplied with fresh tar. Baiiles 56or other means may be provided to remove entrained liquor from thevapors escaping through the outlet 57. 7

The amount of dehydration and distillation which takes place within thetower shown in Fig. '7 will depend upon the quantity of the tar andgases and upon the temperature of the gases. Hot gases may be introducedthrough the inlet 50 from the end of the collector main by means of aconnection such as that shown by pipe l l in Fig. 1, or the gasintroduced into the inlet 50 may be tapped off of the cross-over inainorany other part of the'apparatus from which gases or" The temperature ofthe gases will depend upon the part oithe apparatus from which the gasesare obtained and upon the operation of the coke oven system. Gases takenoff from one end of the collector main through the pipe 'l i, if used insufficient quantity, will be s'ufiiciently hot to completely dehydratethe tar and to distill ofi considerable of the low-boiling constituents.On the other hand, gases taken from the centre box of the collector mainor from the cross-over main will not volatilize such a large percent ofthe lowboiling constituents, and if used in small quantity will no morethan partially dehydrate the tar. By recirculating the tar in the towerthe amount of dehydration and distillation may be increased. The desireddegree of dehydration and .volatilization may be obtained by selectionof gases of the proper-temperature and by proper regulation of thequantity of gas and oil.

Instead of dehydrating coal tar produced at the coke-oven battery wherethe dehydration and distillation are eiTected, tar from other batteries,or from other sources such as gas-house tar or water-gas tar, can besimilarly dehydrated with hot coke-oven gas. In cases Where a mixedproduct is desired, different kinds of tar can be mixed beforedehydration and the mixed tar then dehydrated, or dehydrated anddistilled. Mixtures of water-gas tar and coal tar can thus be employedto give mixed dehydrated products; or mixtures of gas-house tar and coaltar, etc. Mixed oils will also be produced by cooling the gases used fordehydration.

In a similar manner, gas-house tar can be dehydrated or dehydrated anddistilled, by means of hot gas from the gas retorts; and Water-gas tarcan be similarly dehydrated and distilled by means of hot water gas. Theinvention is thus of more or less general application to the dehydrationof tar with the hot coke-oven or other gases, thus utilizing heatcommonly wasted and enabling dehydrated tar to be directly produced atthe same plant at Which water-containing tar is produced.

Instead of dehydrating tar, tarry oils can be similarly dehydrated, forexample, oils such as are produced in the diiierent condensers of abyproduct recovery system where ammonia liquor is employed for throwingdown the tarry oils. By subjecting such oils to dehydration in this way,dehydrated oils can be directly produced at a by-product coke-oven plantWithout the expenditure of fuel for heating and dehydration, and withutilization of the heat contained in the hot coke-oven gases, which iscommonly wasted. In addition to dehydrating such oils, tarry oils, ortars of varying oil content, the dehydration may be combined withdistillation of part of the oil constituents and the distillate can beseparately condensed, thus giving lighter distillate oils and heavierdehydrated residual oils or tars.

I claim:

1. The method of dehydrating tar which comprises passingwater-containing tar to a dehydrating still, bringing hot coaldistillation gases from a coke oven or retort into intimate contact withthe tar in the still while the gases are yet at a temperature suificientto effect substantially complete removal of the water from the tar,regulating the contact of the tar with the gases so that the majorportion of the volatile oils originally present in the tar remains inliquid form, Withdrawing from the still a tar product containing a majorportion of the volatile oils originally present in the tar butsubstantially free from water.

2. The method of dehydrating tar which comprises passingwater-containing tar into a dehydrating still, bringing hot coaldistillation gases from a coke oven or retort into intimate contact withthe tar in the still while the gases are yet at a temperature aboveabout 125 (3., regulating the contact of the tar with the gases so thatwater is removed therefrom and so that the major portion of volatileoils originally present in the tar remains in liquid form, andwithdrawing from the still a dehydrated tar product comprising a majorportion of the volatile oils originally present in the tar.

3. The method of dehydrating tar which comprises passingwater-containing tar into a dehydrating still, bringing hot coaldistillation gases from a coke oven or retort into intimate contact withthe tar in the still while the gases are at a temperature of about 160C., regulating the contact of the tar with the gases so that the majorportion of volatile oils contained in the tar remains in liquid form,and withdrawing from the still a dehydrated tar product comprising amajor portion of the volatile oils originally present in the tar.

4. The method of dehydrating and distilling tar l which comprisesbringing water-containing tar into contact with hot coal distillationgases whereby the tar is dehydrated and distilled, and subjecting theresulting gases with admixed vapors from the dehydration anddistillation to condensation for the recovery of condensableconstituents therefrom and returning condensed oils thus obtained to thetar to give a dehydrated tar containing substantially all of its normaloil constituents.

STUART PARMELEE MILLER.

